When does someone's reading tastes shift from fiction to non-fiction?

After a life spent growing up on science fiction or mystery or adventure, why does someone shift entirely to stories taken from real life?

What shifts inside a psyche that causes it to no longer find escape or inspiration in characters of other times or worlds but in the characters of the World?

It's not that one is "better" than the other. Or more "real" than the other. Or more "substantive" than the other. Not at all.

I so rarely pick up a fiction book any longer. Only when written by the few remaining authors I follow and trust.

Instead, the bookshelves are bending under hardcovers (easier to read the bigger type with these older eyes) about advocates and journalists and suffragists and immigrants and Native Americans and essayists and senators-now-presidents.

Just wondering.